Introduction. The development of the territories of modern cities contributes to the increase in modern urban development and the development of transport and engineering infrastructure. In this regard, the consumption of petroleum products is increasing, which seriously affects the ecological balance of urban areas. In large cities located in hot regions, the most extreme environmental conditions are formed. The growth of modern high-rise buildings, the intensive use of urban transport makes the air pollution of the city more significant. At high temperatures characteristic of southern cities, the pollution of urban space is the most noticeable.

Materials and methods. The paper analyzes the ecology of hot cities in Russia. The most polluted areas of cities were identified, where the concentration of pollutants exceeds the permissible limits due to lack of air exchange. The role of air flows of thermal origin in the aeration of yard spaces is determined.

Results. On the example of a nine-story residential building in the city of Volgograd, an analysis was made of the formation of air flows of thermal origin. description of the applied information materials and scientific methods. A graph of field measurements of the speed of convective flows near the facades of the building at different times of the daylight hours, the regulation of which can improve the ecology of urban areas, is given.

Conclusions. Modern cities with a hot climate, which are characterized by high-rise dense buildings, are in environmentally unfavorable conditions. In the yard spaces, areas with stagnation of air and the concentration of pollutants are formed, due to the violation of the aeration of the territory. The studies carried out are of practical importance and can be used to assess the air exchange of inter-house territories in urban planning and the development of urban spaces. The formation of air flows of thermal origin, considered in the study, can contribute to the air exchange of yard spaces and significantly improve the ecological situation.

Introduction. The paper presents the results of a study of Ryazan apartment buildings built at the turn of the XIX and XX centuries, which are important elements of the historical and architectural environment. The construction of apartment buildings influenced the formation of a new architectural type of urban development; both entire apartment complexes and individual multi-apartment buildings appeared on the city streets. The relevance of the work is due to a number of factors: the lack of comprehensive studies on the stated topic; the rapid disappearance of this type of historical residential architecture; the need to identify the characteristic features of Ryazan two-storey apartment buildings, which are elements of the historical and architectural environment. The purpose of the research is to study the surviving two-storey wooden apartment buildings, identify their planning, functional, volumetric-spatial and architectural-artistic features.

Materials and methods. In order to identify the surviving objects, field surveys with photo recording were conducted. The features of the location of objects in the building structure and their interaction with the surrounding architectural and spatial environment made it possible to identify historical-urban planning and visual-landscape analyses. Scientific works, archival documents and photographic materials were analyzed; graphic materials were compiled and processed.

Results. During the study, 30 surviving two-storey apartment buildings were identified. A comprehensive analysis of the objects made it possible to identify a number of characteristic features of this type of residential pre-revolutionary architecture in the historical centre of Ryazan: location, functional planning solution, variability of volume compositions and decorative solutions.

Conclusions. At the beginning of the XXI century, a large percentage of the old buildings of Ryazan were lost due to the construction of new residential complexes and centres for various purposes. The central and peripheral streets with wooden buildings suffered especially. Each preserved element of the historically formed centre is a unique monument. A special role is played by two-storey wooden houses (formerly tenement houses), which bear characteristic traces of the Ryazan culture of the period of the XIX – early XX centuries.

Introduction. The present paper considers the propagation of seismic waves through a barrier with a memory effect based on integro-differential equations. Conventional wave models, founded upon elastic equations, frequently neglect the viscoelastic characteristics of actual soils and seismic barriers, which possess the capacity to “remember” prior deformations. To achieve a more accurate description of the phenomenon, an integro-differential model with an exponential memory kernel is employed. This model allows for the modelling of a wide range of dissipative effects and the derivation of analytical solutions applicable to seismic protection problems.

Materials and methods. The model is predicated on integro-differential equations of motion, which take into account the deformation history and material relaxation. Direct and inverse Fourier and Laplace transforms are applied in order to obtain analytical solutions. Two forms of pulses are investigated: the delta function and the Gaussian pulse.

Results. In the context of a delta pulse, supplementary “tails” and bursts are formed within the medium that exhibits memory, with the kernel parameters (α and β) exerting an influence on the rate of “forgetting” and its intensity. In the case of a Gaussian pulse, the introduction of memory effects results in a more gradual blurring of the waveform, accompanied by the acquisition of additional distortions, particularly at high values of α and during slow memory decay β. It has been demonstrated that by manipulating the values of α and β, a substantial alteration in the nature of the interaction can be achieved, resulting in either a sharp local peak or a more uniform distribution, characterized by significant energy dissipation.

Conclusions. This study demonstrates the importance of taking into account the “memory effect” when modelling seismic barriers. Integro-differential equations with an exponential kernel facilitate a more precise description of the processes of attenuation, energy dissipation and transformation of seismic wave shape in real ground conditions. The analytical solutions obtained from this study form a foundation for the design of more efficient seismic barriers, capable of “tuning” to the required range of vibration frequencies.

Introduction. Currently, composite structures are a rapidly developing and promising area of monolithic reinforced concrete construction. The increasing use of combined structures and some features of their resistance at the stages of manufacture and operation arouse the natural interest of researchers in establishing the real stress-strain state at all stages of the life cycle of the structure. The aim of the work was to study the effect of the initial deflection of the profiled sheeting at the concreting stage on the strength of composite slabs at the operation stage. The object of the study was single-span orthotropic composite floor slabs made on permanent formwork in the form of profiled sheeting grades H75, H144, H153 according to GOST 24045–2016 and TRP200 according to GOST R 52246, 0.7–0.9 mm thick. The subject of the study was the strength of the composite slab, taking into account the pre-operational state of the structure.

Materials and methods. The study used a calculation and analytical research method based on regulatory documents in force in the Russian Federation.

Results. The values of additional bending moments and shear forces in composite slabs at the operational stage caused by the primary deflection of the corrugated sheet at the concreting stage were determined. The dependences of the acting forces on the span dimensions and the useful load value for various grades of corrugated sheets were revealed. The analysis of the research results was implemented in graphical and tabular forms. The data obtained for the most common grades of corrugated sheets and slab spans at various load levels indicate the need to increase the working reinforcement of the slabs in relation to the initial reinforcement.

Conclusions. Based on the results of the study, a conclusion was made on the need to carry out clarifying strength calculations, taking into account the geometric nonlinearity of the structure, at the operational stage due to the overload of the corrugated sheet with concrete mix during concreting due to the development of initial deflections. With slab spans greater than 3.5 m and useful loads over 3 kPa, the deflection at the concreting stage due to the action of the increased weight of the concrete mix leads to the need to install additional longitudinal reinforcement in the ribs of the slab. The obtained data can be used in the design of composite concrete floor slabs and in assessing the technical condition of composite concrete slabs.

Introduction. Connections of steel construction elements are made using rivets, bolts and welding. To fasten thin sheet steel membrane sheathing, especially galvanized, high-strength dowels can be used as a connection element, installed by means of gunpowder charges or pressing into pre-made holes in the elements to be connected.

Materials and methods. Experimental studies were carried out using three types of specimens. The specimens consisted of 0.5 and 0.7 mm thick galvanized steel sheets, which were fixed to a 3 mm thick steel plate using 3 mm high-strength dowels. The possibility of using these dowels with 6 and 10 mm thick steel plates was considered, including into pre-drilled holes with a diameter of 2 mm.

Results. Dowels with a diameter of 3 mm pierced a steel plate with a thickness of 3 mm and firmly fixed a galvanized sheet with a thickness of 0.5 and 0.7 mm. The failure pattern of the specimens depending on the number and location of the dowels was determined. With two dowels, the steel galvanized sheet was observed to fail in the area of the dowels. At four dowels the galvanized steel sheet was destroyed outside the dowel joint in the form of steel plat.rupture. It was found that the full length of 3 mm diameter dowels did not fit into the 6 and 10 mm thick plates. When holes with diameters of 2, 2.5 and 3 mm are made in these plates, the full length of the dowels can be installed.

Conclusions. Experimental studies of dowel joints of thin-sheet galvanized steel have shown that even household dowels have high strength and stability of parameters and can be used to connect load-bearing elements of steel structures.

Introduction. In numerical modelling of mechanical systems, the proximity of the computational model to the actual behaviour of the object is largely determined by the adequacy of the specified boundary conditions. In practice, the support conditions of structural elements often differ from the idealized assumptions adopted in computational models, which leads to discrepancies between calculated and experimental data.

Materials and methods. This study considers an approach to optimizing the boundary conditions of a finite element model using the evolutionary algorithm CMA-ES [1]. The object of investigation was a spatial frame structure, for which experimental studies of dynamic characteristics — natural frequencies and free vibrations — were conducted. The comparison of calculated and experimental frequencies and vibration modes was performed using the modal assurance criterion (MAC) and the relative error between the calculated eigenfrequencies of the model and their experimentally determined values. Based on these metrics, the objective function of the optimization problem was formulated.

Results. The optimization made it possible to determine the stiffness coefficients of the support connections in the lower chord of the structure in six degrees of freedom. The results showed that the application of the evolutionary approach significantly reduced discrepancies between model and experimental data, thereby improving the accuracy of the computational model.

Conclusions. The accuracy of finite element modelling of structures can be improved by aligning the model and experimental dynamic characteristics through the use of evolutionary algorithms.

Introduction. Due to the constant increase in design-exceeding technogenic and natural impacts on buildings and structures, an important direction for improving their safety is to conduct experimental research on structural elements designed to protect against such impacts. The most critical components of these structural systems are the connection joints between their elements, which must ensure the safety of the frames under various, including extreme, conditions. This necessitates a more comprehensive assessment of their crack resistance under special impacts.

Materials and methods. The experimental study was conducted on a specially designed test setup capable of simulating the stress-strain state of a beam both under service conditions and under emergency impacts. During the test, at various stages of loading with the design load and after the emergency impact, the following parameters were measured: strains in the concrete and reinforcement, vertical and horizontal displacements of the joint elements. The pattern of crack formation, propagation, and width was also recorded.

Results. A study was conducted on the connection joints of heavy concrete bar elements under static and static-dynamic loading. The results of experimental investigations into crack resistance, as well as the development, width, and patterns of crack formation in the connection nodes under these loading conditions, are presented.

Conclusions. The study results indicated a similar pattern of crack formation in the connection joints of beams and columns under both static and static-dynamic loading. A difference was observed in the location of flexural cracks in the columns, which is explained by the multi-stage nature and the time interval of the static load application.

Introduction. Global warming and the cement industry’s significant contribution to carbon dioxide emissions (7–8 % of the total) make the search for environmentally friendly alternatives to Portland cement an urgent challenge. One of the most promising alternatives is geopolymers — heat-free binders produced through the alkaline activation of aluminosilicate raw materials. Geopolymers outperform conventional cement in terms of energy efficiency, resource conservation, and environmental performance, and their structure and chemical composition fundamentally differ from those of traditional cements. The use of geopolymers in construction can substantially reduce costs and improve the environmental situation in the regions.

Materials and methods. The materials investigated included fly ash, ash-and-slag mixture, ground granulated blast-furnace slag, potassium and sodium silicate solutions used for the preparation of the geopolymer binder. An IR 5081-5 press was employed to determine the strength of the binder specimens, while the strength of geopolymer concrete was tested using a TP-1-350 press. Frost resistance was evaluated using an accelerated method in a climate chamber. Water permeability was determined with an AGAMA-2PM testing apparatus.

Results. The study presents the results of a comprehensive investigation into the selection of geopolymer binder and concrete compositions as alternatives to conventional heavy concrete based on cement binders. The developed geopolymer concrete compositions correspond to concrete strength classes B15, B20, B22.5, B25, and B30. The effect of heat and moisture treatment on the strength characteristics of the geopolymer binder was examined.

Conclusions. Chemical and physico-mechanical analyses of the geopolymer binder components were carried out. The influence of the type of silicate solution and of the heat-and-moisture curing regime on the binder strength was investigated. Rational compositions of geopolymer binders and corresponding concretes were developed. Test results on water resistance, compressive and flexural strength, porosity, and frost resistance were obtained, and the workability of geopolymer mixtures (cone slump) was evaluated. According to the findings, geopolymer binder compositions up to class B30 can be successfully applied in the construction industry as an environmentally friendly alternative to Portland-cement concretes.

Introduction. Dry building mixes based on hydraulic binders are currently widely used. The use of dry mixes is multifaceted and is mainly associated with the preparation of solutions and fine-grained concrete. These mixes are obtained by regulating rheological and physical-mechanical properties by introducing modifying additives and microfillers in the form of glass microspheres.

Materials and methods. Polymer and basalt fibre were used to regulate the properties of the mix at the microscopic level, thereby creating a strengthened reinforced microstructure of hardened fine-grained concrete. The compositions of dry mixes based on polymer and basalt fibre were selected using a superplasticizer and 10 % coated hollow glass microspheres
of the MS-VP-A9 brand. A dry mix based on the specified composition with the use of superplasticizers, glass microsphe-res, and basalt or polymer fibre is prepared by mixing and grinding in a linear induction rotator, which has an alternating field inductance of 0.2 T and a frequency of 50 Hz. The mixture is processed for 240 seconds. Polymer and basalt fibres were introduced into the dry mix separately, i.e. only one of the two presented types of fibres was used in each composition.

Results. Dry mixes activated in an electromagnetic field were mixed with water in the amount necessary to obtain solutions of equal mobility. The solution was prepared for 4–5 minutes, while the resulting mixtures had increased plasticity and homogeneity with an equal amount of mixing water, in comparison with the control compositions, without the use of basalt or polymer fibres.

Conclusions. The influence of the type and quantity of fibre on the physical and mechanical properties of fine-grained concrete obtained on the basis of dry building mixtures activated by electromagnetic treatment was determined.

Introduction. The article discusses the conceptual foundations of the model of a thermogravitational ventilation system for residential buildings, based on the study of buildings with low ventilation needs in climate conditions where the temperature difference between indoor and outdoor air is great. Gravity ventilation is considered in the context of the thermal regime of walls in the course of insolation of building facades erected in regions with predominantly high solar heat fluxes.

Materials and methods. A method involving a database of hydrometeorological reference books was used to analyse and monitor the sunlight and wind regime in the countries with extended warm seasons. The process of natural ventilation was studied in the Revit program using methods of sunlight analysis of structural shells of buildings; field studies of insolation and thermal regimes were also employed.

Results. A theoretical proposition was developed for the thermogravitational ventilation of buildings in areas featuring long warm seasons. A physical and mathematical model of a thermogravitational ventilation system was devised; it describes a natural process of indoor air circulation based on a difference in the air density inside and outside buildings. An integrated approach was applied to study the mechanism of natural aeration of apartments; full-scale experimental studies were conducted; mathematical models of microclimate and thermophysical processes were developed; software and thermal imaging surveys were employed.

Conclusions. The author’s theoretical proposition, developed for thermogravitational ventilation in buildings erected in areas with long warm seasons, enables researchers to devise a physical and mathematical model of a thermogravitational ventilation system of buildings, describing the natural process of indoor air circulation based on a difference in indoor and outdoor air density. In general, thermogravitational ventilation is an effective and environmentally friendly solution for natural air exchange, because it maintains a comfortable indoor air regime, especially in low-wind and calm environments.

Introduction. Within the federal programme “Creating a Network of Modern University Campuses” new campuses are being developed through public-private partnerships (PPP). A campus is treated as a multi-level socio-economic system that simultaneously generates educational, scientific-technological and entrepreneurial value. The effectiveness of managing such a system can be demonstrated only through an integrated indicator framework that objectively captures the performance of the three primary actors — the public partner, the private partner and the university — in pursuing the project’s shared strategic goals.

Materials and methods. The aim of this study is to develop an approach for defining a set of performance metrics to evaluate the effectiveness of joint campus management in projects implemented through public-private partnership mechanisms, taking into account the interests of the public partner, private partner and the university. The research employs methods of legal and regulatory analysis, comparative case studies of domestic and international university campuses and content analysis of Russian and international publications.

Results. The analysis of existing approaches reveals a shift in campus management focus — from physical infrastructure to the creation of competitive advantages stemming from activities carried out within the campus. The applicability of the product-service approach to achieving campus competitiveness is justified, which is determined by the quality of the developed product portfolio, taking into account the development goals, potential and competencies of the regional government, private investor and university. The study proposes an approach to defining a set of metrics that enables the evaluation of joint campus management performance, comparison of academic, infrastructural, and regional socio-economic outcomes, timely identification of imbalances in the target product development model and justification of managerial decisions aimed at aligning stakeholder interests. The developed approach can be applied in the design of metric systems for individual
PPP-based campus projects, serving as a management tool that supports investment return, achievement of academic goals and enhancement of regional socio-economic impact.

Conclusions. The competitiveness of a PPP-based campus equals the competitiveness of its product portfolio, shaped at the intersection of three interdependent domains: university operations, infrastructure quality and regional potential. Achieving product portfolio competitiveness requires managing processes that generate competitive advantages through the coordinated efforts of all key stakeholders — the public partner, private partner, and the university.

Introduction. Despite the significant scale and importance of the heat supply sector for the country’s housing and public utilities, a number of persistent issues have accumulated in its operation, reducing both its reliability and economic efficiency. This underscores the need to identify directions for enhancing the performance and dependability of heat supply systems through the rational use of energy resources and to develop a comprehensive system of performance indicators. In line with Russia’s strategic policy documents, energy conservation is a priority for the development of the national energy sector, including urban heat supply, which creates opportunities to improve system reliability by reducing failures across networks and sources and to enhance cost-effectiveness through the rational use of energy resources.

Materials and methods. The research applied logical analysis and systematisation methods. An analysis of publicly available data sources and expert studies in the field of heat supply made it possible to summarise and systematise practical experience in implementing energy-saving measures across the generation, transmission, and consumption stages of thermal energy.

Results. A comprehensive set of measures aimed at improving the reliability and cost-effectiveness of heat supply through the rational use of energy resources has been developed and systematised. In addition, a framework of performance indicators has been designed to assess the effectiveness of heat-supply operations in the urban and municipal sectors, reflecting improvements in reliability and cost-effectiveness resulting from the proposed measures.

Conclusions. Implementing the proposed energy-conservation and energy-efficiency measures across the stages of heat generation, transmission, and consumption will enhance both the reliability and cost-effectiveness of urban and municipal heat-supply systems. The suggested system of performance indicators will enable a comprehensive evaluation of the effectiveness of these measures in terms of the improvements achieved.